Composite materials are being used in an increasing variety of applications. For example, composite materials are being used to replace metals in many applications. Using composite materials to replace metals can have significant benefits, such as reduced weight. However, there are often differences between material properties of metals and material properties of composite materials used to replace them. For example, certain material properties of composite materials may be anisotropic. To illustrate, a composite material may have electrical properties that vary by location or direction.
Anisotropic electrical properties can make replacing metals with composite materials problematic. For example, commercial aircraft have traditionally used metal skins. Metal skins provide more or less uniform electrical properties, which can help distribute charge evenly in the event of a lightning strike. Forming aircraft skins of composite materials can reduce aircraft weight; however, the composite materials tend to conduct anisotropically. Anisotropic conduction may lead to localized hotspots in the event of a lightning strike, which can cause significant damage, such as delamination of the composite material.
Aircraft manufacturers and regulatory agencies use considerable care in selecting and testing composite materials used for aircraft skins. Generally, testing is performed by applying simulated lightning strikes to assemblies of components including composite materials (e.g., a composite panel with metal connectors). Testing a large variety of materials, assembly processes, and other components (e.g., connectors) in this manner is time consuming and expensive.